This invention relates to a speed sensing assembly for a vehicle adaptive braking system.
Speed sensing assemblies, which measure the rate of rotation of a vehicle wheel, are critical components of vehicle adaptive braking systems. However, prior art speed sensor designs, although many have worked acceptably, have not been as trouble-free as desired, since most of the prior art speed sensors have consisted of separate rotor and stator assemblies which must be separately installed on a vehicle. In most designs, such as that shown in U.S. Pat. Nos. 3,988,624 and 3,626,226, the critical air gap between the sensing head and the rotor must be set at the time the speed sensor is installed on the vehicle. Even in prior art devices such as disclosed in U.S. patent application Ser. No. 481,938, filed June 21, 1974, owned by the assignee of the present invention, in which the air gap between the sensing head and the rotor is preset when the speed sensor is manufactured, the sensing assembly must be installed separately in the vehicle axle and the vehicle hub cap must be installed separately to transmit rotation of the vehicle wheel to the sensor assembly. The present invention, however, solves most of the problems inherent in prior art speed sensor assemblies, in that the hub cap and sensor unit are a one-piece assembly, which is installed on the vehicle in the same manner as hub caps alone are installed, and requires no attention or adjustment at the time that it is installed upon the vehicle.